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Natural oil polyols

Natural oil polyols

2019年12月26日
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Natural oil polyols, also known as NOPs or biopolyols, are polyols derived from vegetable oils by several different techniques. The primary use for these materials is in the production of polyurethanes. Most NOPs qualify as biobased products, as defined by the United States Secretary of Agriculture in the Farm Security and Rural Investment Act of 2002.

NOPs all have similar sources and applications, but the materials themselves can be quite different, depending on how they are made. All are clear liquids, ranging from colorless to medium yellow. Their viscosity is also variable and is usually a function of the molecular weight and the average number of hydroxyl groups per molecule (higher mw and higher hydroxyl content both giving higher viscosity.) Odor is a significant property which is different from NOP to NOP. Most NOPs are still quite similar chemically to their parent vegetable oils and as such are prone to becoming rancid. This involves autoxidation of fatty acid chains containing carbon-carbon double bonds and ultimately the formation of odoriferous, low molecular weight aldehydesketones and carboxylic acids. Odor is undesirable in the NOPs themselves, but more importantly, in the materials made from them.

There are a limited number of naturally occurring vegetable oils (triglycerides) which contain the unreacted hydroxyl groups that account for both the name and important reactivity of these polyols. Castor oil is the only commercially available natural oil polyol that is produced directly from a plant source: all other NOPs require chemical modification of the oils directly available from plants.

The hope is that using renewable resources as feedstocks for chemical processes will reduce the environmental footprint[1] by reducing the demand on non-renewable fossil fuels currently used in the chemical industry and reduce the overall production of carbon dioxide, the most notable greenhouse gas. One NOP producer, Cargill, estimates that its BiOH(TM)polyol manufacturing process produces 36% less global warming emissions (carbon dioxide), a 61% reduction in non-renewable energy use (burning fossil fuels), and a 23% reduction in the total energy demand, all relative to polyols produced from petrochemicals.[2]

Sources of natural oil polyols

Ninety percent of the fatty acids that make up castor oil is ricinoleic acid, which has a hydroxyl group on C-12 and a carbon-carbon double bond. The structure below shows the major component of castor oil which is composed of the tri-ester of rincinoleic acid and glycerin:

Major component of castor oil

Other vegetable oils – such as soy bean oil,[3] peanut oil, and canola oil – contain carbon-carbon double bonds, but no hydroxyl groups. There are several processes used to introduce hydroxyl groups onto the carbon chain of the fatty acids, and most of these involve oxidation of the C-C double bond. Treatment of the vegetal oils with ozone cleaves the double bond, and esters or alcohols can be made, depending on the conditions used to process the ozonolysis product.[4] The example below shows the reaction of triolein with ozone and ethylene glycol.

Ozonolysis of unsaturated triglyceride

Air oxidation, (autoxidation), the chemistry involved in the "drying" of drying oils, gives increased molecular weight and introduces hydroxyl groups. The radical reactions involved in autoxidation can produce a complex mixture of crosslinked and oxidized triglycerides. Treatment of vegetable oils with peroxy acids gives epoxides which can be reacted with nucleophiles to give hydroxyl groups. This can be done as a one-step process.[5] Note that in the example shown below only one of the three fatty acid chains is drawn fully, the other part of the molecule is represented by "R1" and the nucleophile is unspecified. Earlier examples also include acid catalyzed ring opening of epoxidized soybean oil to make oleochemical polyols for polyurethane foams [6] and acid catalyzed ring opening of soy fatty acid methyl esters with multifunctional polyols to form new polyols for casting resins.[7]

Epoxidation and ring opening of unsaturated triglyceride

Triglycerides of unsaturated (containing carbon-carbon double bonds) fatty acids or methyl esters of these acids, can be treated with carbon monoxide and hydrogen in the presence of a metal catalyst to add a -CHO (formyl) groups to the chain (hydroformylation reaction) followed by hydrogenation to give the needed hydroxyl groups.[8] In this case R1 can be the rest of the triglyceride, or a smaller group such as methyl (in which case the substrate would be similar to biodiesel). If R=Me then additional reactions like transesterification are needed to build up a polyol.

Hydroformylation and reduction of unsaturated triglyceride

Uses

Castor oil has found numerous applications, many of them due to the presence of the hydroxyl group that allows chemical derivatization of the oil or modifies the properties of castor oil relative to vegetable oils which do not have the hydroxyl group. Castor oil undergoes most of the reactions that alcohols do, but the most industrially important one is reaction with diisocyanates to make polyurethanes.

Castor oil by itself has been used in making a variety of polyurethane products, ranging from coatings to foams, and the use of castor oil derivatives continues to be an area of active development. Castor oil derivatized with propylene oxide[9] makes polyurethane foam for mattresses and yet another new derivative is used in coatings [10]

Apart from castor oil, which is a relatively expensive vegetable oil and is not produced domestically in many industrialized countries, the use of polyols derived from vegetable oils to make polyurethane products began attracting attention beginning around 2004. The rising costs of petrochemical feedstocks and an enhanced public desire for environmentally friendly green products have created a demand for these materials.[11] One of the most vocal supporters of these polyurethanes made using natural oil polyols is the Ford Motor Company, which debuted polyurethane foam made using soy oil in the seats of its 2008 Ford Mustang.[12][13] Ford has since placed soy foam seating in all its North American vehicle platforms. The interest of automakers is responsible for much of the work being done on the use of NOPs in polyurethane products for use in cars, for example is seats,[14][15] and headrests, armrests, soundproofing, and even body panels.[16]

One of the first uses for NOPs (other than castor oil) was to make spray-on polyurethane foam insulation for buildings.[17

]

NOPs are also finding use in polyurethane slab foam used to make conventional mattresses[8] as well as memory foam mattresses.[18][19]

The characteristics of NOPs can be varied over a very wide range. This can be done by selection of the base Natural Oil (or oils) used to make up the NOP. Also, using known and increasingly novel (Garrett & Du) chemical techniques, it is possible to graft additional groups onto the triglyceride chains of the NOP and change its processing characteristics and this in turn will change and modify in a controlled manner, the physical properties of the final article which the NOP is being used to produce. Differences and modifications in the process regime and reaction conditions used to make a given NOP also generally lead to different chemical architectures and therefore different end use performance of that NOP; so that even though two NOPs may have been made from the same Natural Oil root, they may be surprisingly different when used and, will produce a detectably different end product too. Commercially, (since 2012) NOPs are available and made from; sawgrass oil, soybean oil, castor oil (as an grafted NOP), rapeseed oil, palm oil (kernel and mesocarp), and coconut oil. There is also some work being done on NOPs made from Natural Animal oils.

Initially in the US, and since early 2010, it has been routinely possible to replace over 50% of petrochemical-based polyols with NOPs for use in slab foams sold into the mass market, furniture and bedding industries. The commercialised technology [20] also eliminates or greatly reduces the odor problem, mentioned above, normally associated with the use of NOPs. This is particularly important when the NOP is to be used at ever higher percentage levels, to try to reduce dependency on petrochemical materials, and to produce materials for use in the domestic and contract furniture segments which are historically very sensitive to "chemical" odors in the final foam product in people's homes and places of work.

Amongst other useful effects of using high levels of Natural Oil Polyols to make foams are the improvements seen in the long-term performance of the foam under humid conditions and also on the flammability of the foams; compared to equivalent foams made without the presence of the NOP. People perspire; and so foams used for the construction of matrasses or furniture will, over time, tend to feel softer and give less support. The perspiration gradually softens the foam. Foams made with high levels of NOPs are much less prone to this problem, so that the useful lifetime of the upholstered product can be extended. The use of high levels of NOP also make it possible to manufacture foams with flame retardants which are permanent, and therefore are not later emitted into the household or work place environment. These relatively recently developed materials can be added at very low levels to NOP foams to pass such well known tests as California Technical Bulletin 117, which is a well-known flammability test for furniture. These permanent flame-retardants are halogen free and key into the foam matrix and are therefore fixed there. An additional effect of using these new, highly efficient, permanent flame retardants, is that the smoke seen during these standard fire tests, may be considerably reduced compared to that produced when testing foams made using non-permanent flame retardant materials, which do not key themselves into the foam structure.[21] More recent work during 2014 with this "Green Chemistry" has shown that foams containing about 50 percent by weight of natural oils can be made which produce far less smoke when involved in fire situations. The ability of these low emission foams to reduce smoke emissions by up to 80% is an interesting property which will aid escape from fire situations and also lessen the risks for first responders i.e. emergency services in general and fire department personnel in particular.[22]

Other technology can be combined with these flammability characteristics to give foams, which have extremely low overall emissions of volatile organic compounds, known as VOCs.

天然油多元醇

2019年12月26日
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天然油多元醇,也称为NOP或生物多元醇,是通过几种不同技术衍生自植物油的多元醇这些材料的主要用途是生产聚氨酯根据美国农业部长在2002年《农场安全和农村投资法》中的定义,大多数NOP都属于生物基产品

NOP都具有相似的来源和应用,但是材料本身可能会完全不同,这取决于它们的制作方式。都是透明液体,从无色到中等黄色。它们的粘度也是可变的,并且通常是分子量每个分子的平均羟基数的函数(较高的mw和较高的羟基含量均提供较高的粘度。)气味是重要的性质,不同于NOP至NOP。大多数NOP在化学上仍与其母体植物油非常相似,因此很容易变这涉及自氧化含有碳-碳双键的脂肪酸链的形成,最终形成有臭的,低分子量的羧酸臭味在NOP本身中是不可取的,但更重要的是,在它们制成的材料中是不可闻的。

有限数量的天然植物油(甘油三酸酯)含有未反应的羟基,这些羟基说明了这些多元醇的名称和重要的反应活性。蓖麻油是唯一可直接从植物来源生产的市售天然油多元醇:所有其他NOP都需要对可直接从植物中获得的油进行化学改性。

希望通过将可再生资源用作化学过程的原料,可以减少对化学工业目前使用的不可再生化石燃料的需求,并减少二氧化碳(最著名的温室气体)的总体产量,从而减少环境足迹[1]一家NOP生产商,嘉吉(Cargill)估计,其BiOH(TM)多元醇生产工艺可减少36%的全球变暖排放量(二氧化碳),将不可再生能源的使用量减少61%(燃烧化石燃料),并将二氧化碳排放量减少23%。总能源需求,全部与石化产品生产的多元醇有关

 

天然油多元醇的来源

构成蓖麻油的脂肪酸的90%蓖麻油酸,其在C-12上具有羟基并具有碳-碳双键。以下结构显示了由蓖麻油酸和甘油的三酯组成的蓖麻油的主要成分

 

Major component of castor oil

其他植物油-例如豆油,[3] 花生油和低芥酸菜子油 -含有碳-碳双键,但没有羟基。有几种用于将羟基引入脂肪酸碳链上的方法,其中大多数涉及CC双键的氧化臭氧处理植物油会裂解双键,并且可以制备酯或醇,具体取决于用于处理臭氧分解产物的条件[4]下例显示了三油精与臭氧和乙二醇的反应

 

Ozonolysis of unsaturated triglyceride

空气氧化(自氧化)是干燥油 “干燥”所涉及的化学反应,分子量增加,并引入羟基。自动氧化中涉及自由基反应可产生交联和氧化的甘油三酸酯的复杂混合物。过氧酸处理植物油得到环氧化物,可以与亲核试剂反应得到羟基。这可以一步一步完成。[5]注意,在下面显示的示例中,只有三个脂肪酸链中的一个被完全绘制,分子的另一部分由“ R 1且亲核试剂未作具体说明。较早的例子还包括环氧化大豆油的酸催化开环以制备聚氨酯泡沫的油性多元醇[6],以及大豆脂肪酸甲酯与多功能多元醇的酸催化开环以形成用于铸造树脂的新多元醇。 

Epoxidation and ring opening of unsaturated triglyceride

可以在金属催化剂存在下,一氧化碳氢气不饱和(含有碳-碳双键)脂肪酸的甘油三酸酯或这些酸的甲基酯上进行处理,以在链上添加-CHO(甲酰基)基团(加氢甲酰化反应) ),然后氢化得到所需的羟基。[8]在这种情况下,R 1可以是甘油三酸酯的其余部分,也可以是较小的基团,例如甲基(在这种情况下,底物将类似于生物柴油)。如果R = Me,则需要另外的反应如酯交换反应以建立多元醇。

Hydroformylation and reduction of unsaturated triglyceride

蓖麻油已经发现了许多应用,其中许多是由于羟基的存在,相对于不具有羟基的植物油,其允许油的化学衍生或改变蓖麻油的性能。蓖麻油经历醇所进行的大部分反应,但是工业上最重要的反应是与二异氰酸酯反应以制备聚氨酯。

蓖麻油本身已被用于制造从涂料到泡沫的多种聚氨酯产品,并且蓖麻油衍生物的使用继续是积极发展的领域。环氧丙烷衍生化的蓖麻油[9] 制造用于床垫的聚氨酯泡沫,而另一种新的衍生物用于涂料[10]

除了蓖麻油(蓖麻油是一种相对昂贵的植物油,而且在许多工业化国家都不在国内生产)以外,从2004年开始,使用源自植物油的多元醇生产聚氨酯产品开始引起人们的关注。石化原料的成本不断上涨,成本不断攀升。公众对环保 绿色产品的需求创造了对这些材料的需求。[11]福特汽车公司是使用天然油多元醇制得的这些聚氨酯中最有声望的支持者之一,该公司在其2008年福特野马的座椅上首次推出了用大豆油制成的聚氨酯泡沫[12] [13]此后,福特在其所有北美汽车平台上均采用了大豆泡沫座椅。汽车制造商的兴趣是在汽车用聚氨酯产品中使用NOP的大部分工作的原因,例如座椅,座椅[14] [15]以及头枕,扶手,隔音甚至车身面板。[16]

NOP(蓖麻油除外)的最初用途之一是制造用于建筑的喷涂聚氨酯泡沫保温材料。

 

]

NOPs也可用于制造常规床垫[8]的聚氨酯平板泡沫以及记忆海绵床垫。[18] [19]

NOP的特性可以在很宽的范围内变化。这可以通过选择用于组成NOP的基础天然油(或多种油)来完成。而且,使用已知的和日益新颖的(Garrett&Du)化学技术,有可能将其他基团接枝到NOP的甘油三酸酯链上并改变其加工特性,从而以受控的方式改变和改变物理性质NOP用于生产的最终产品的一部分。用于制备给定NOP的工艺方案和反应条件的差异和修改通常也会导致不同的化学结构,从而导致该NOP的最终使用性能不同;因此,即使两个NOP可能是从同一天然油的根中制成的,但使用时它们可能会出乎意料地不同,并且,也会产生不同的最终产品。在商业上,(自2012年起)NOP可用并由其制造;锯草油,大豆油,蓖麻油(作为接枝的NOP),菜籽油,棕榈油(仁和中果皮)和椰子油。关于使用天然动物油制得的NOP的工作也正在进行中。

最初在美国,从2010年初开始,通常可以用NOP代替50%以上的石油化工基多元醇,用于在大众市场,家具和床上用品行业中销售的平板泡沫。商业化技术[20]还消除或大大减少了通常与使用NOP有关的上述气味问题。当要以更高的百分比水平使用NOP,试图减少对石化材料的依赖性以及生产用于历史上对“化学”气味非常敏感的家用和订制家具领域的材料时,这一点尤其重要。人们家中和工作场所中最终的泡沫产品。

使用高含量的天然油多元醇制备泡沫的其他有益效果包括在潮湿条件下泡沫的长期性能以及泡沫的可燃性方面的改进。与不使用NOP制成的同等泡沫相比。人们出汗;因此,用于制造垫子或家具的泡沫会随着时间的流逝而变得更柔软并提供较少的支撑。汗水逐渐软化了泡沫。用高水平的NOP制成的泡沫不太容易出现此问题,因此可以延长软垫产品的使用寿命。使用高水平的NOP还可以制造具有永久性阻燃剂的泡沫,因此以后不会排放到家庭或工作场所环境中。加利福尼亚技术公告117,这是众所周知的家具易燃性测试。这些永久性阻燃剂不含卤素,并键入泡沫基质中​​,因此固定在那里。使用这些新型高效永久性阻燃剂的另一个效果是,与测试使用非永久性阻燃材料制成的泡沫相比,这些阻燃剂在标准防火测试中所观察到的烟雾可以大大减少。自己变成泡沫结构。[21]2014年,有关“绿色化学”的最新工作表明,可以制成含有约50%重​​量百分比的天然油的泡沫,这种泡沫在发生火灾时产生的烟雾少得多。这些低排放泡沫能够减少多达80%的烟雾排放,这是一项令人着迷的特性,它将有助于避免火灾情况的发生,并降低急救人员(即一般的紧急服务人员,尤其是消防部门人员)的风险。[22]

可以将其他技术与这些可燃性相结合,以制成泡沫,该泡沫的挥发性有机化合物(VOC)的总体排放极低。

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